Wellhead assembly



Feb. 1965 G. D. JOHNSON ETAL 3,158,337

WELLHEAD ASSEMBLY Filed Nov. 28. 1960 IN 1' r W l q: a

FIG. 2

ufl] INVENTORSZ I G. D. JOHNSON B. J. WATKINS BY: e /{1,4 0

THEIR AGENT United States Patent Office 3,lh8,337 Patented Feb. 2, 19653,168,337 WELLHEAD ASSEMBLY Glenn D. Johnson, Compton, and Bruce J.Watkins, West Covina, Calif., assignors to Shell (Bil Company, New York,FLY a corporation of Delaware Filed Nov. 28, 196i Ser. No. 72,168 8laims. (Cl. 285-133) This invention relates to a wellhead assembly forclosing the top of oil and gas wells and pertains more particularly to aWellhead assembly especially adapted to be employed underwater at thetop of a well at offshore locations for suspending tubing and casingwithin the well.

A recent development in the oil industry is the drilling and producingof offshore wells wherein the wellhead assembly and production fiowlinesare positioned below the surface of the water, preferably on or near theocean floor so as not to be subjected to the major wind and wave forcesand to be out of the Way of boats that may navigate in that area. Mostoffshore well drilling operations of this type are conducted from aplatform or anchored barge from which the various pieces of equipment,used in or on the well, are lowered through the water from the barge totheir position near the ocean floor. When operating at water depths orat locations where a diver cannot be employed to assemble the equipmenton the ocean floor, it is necessary to provide apparatus that may belowered through the water from a remote station, and then aligned andconnected to other pieces of equipment at the ocean floor.

When installing equipment at the top of an underwater well by the methoddescribed in copending application, Serial No. 24,558, filed April 25,1960, now patent No. 3,099,316, it is preferred that the wellheadassembly be designed so that no fluid flowlines be connected to lateraldischarge ports in the wellhead as this would interfere with the use ofcertain equipment used in installing or removing the wellhead from thetop of the well. Wellheads have to be opened or removed at certain timesin order to carry out workover operations within the well, or in orderto replace a tubing or casing string therein. Presently known wellheadsall employ at least one laterally directed flowline which wouldinterfere with certain underwater operations carried out at thewellhead.

It is therefore a primary object of the present invention to provide awellhead in which the flow from a plurality of pipe strings suspendedtherein is directed vertically out of the wellhead.

Another object of the present invention is to provide a Wellhead forunderwater installations which permits a production tree to be stabbedinto the top of a wellhead in a fluidtight manner.

A further object of the present invention is to provide a Wellheadwherein at least one production tubing string is nested within a casingin a concentric manner, with flow from the concentrically mounted tubingand easing strings leaving the top of the wellhead throughparallelly-arranged flowlines that extend vertically from the top of thewellhead.

Still another object of the present invention is to provide a wellheadhaving a housing made up of a plurality of sections seated one on theother and secured together by substantially horizontally-directedconnector elements.

Another object of the present invention is to provide a wellheadassembly for hanging a casing string and a tub ing string therein withmeans for holding down the tubing and casing string hangers in afluidtight manner within the wellhead.

Still a further object of the present invention is to provide amultiple-section wellhead having aligning means for aligning one sectionwith respect to the other.

These and other objects of this invention will be understood from thefollowing description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view of the wellhead of the present inventionshown in partial longitudinal crosssection; and

FIGURE 2 is a schematic view of a drilling head adapted to replace theupper or bonnet section of the wellhead of FIGURE 1.

In FIGURE 1 of the drawing, numeral 11 represents a surface casing orconductor pipe which has been installed in a well in the ground andpreferably cemented therein in a conventional manner. At the time thesurface casing is positioned in place, a wellhead or casingheadinaccordance with the present invention has been fixedly secured to thetop of the surface casing in any suitable manner such as by welding orby threading. In the particular arrangement of the wellhead shown in thedrawing, the wellhead comprises lower, intermediate and top sections 12,13 and 14, respectively, of a housing which forms the wellhead of thepresent invention. The lower section 12 of the housing is preferablyprovided with a support base 15 which is fixedly secured to the lowersection as by welding. The support base 15 in turn may rest on a cementfoundation (not shown) or any other suitable foundation or base placedaround the well.

The lower section 12 of the housing of the wellhead is provided with asloping shoulder 16 adapted to seat and receive thereon a cooperatingportion of a casing hanger 17 which is normally provided with suitableseals 18. The casing hanger 17 is employed to support a string of wellcasing 21 within the surface casing 11. The interior wall of the casinghanger 17 is provided with suitable means, for example, a left-handthread by which the casing hanger 17 could be attached to the lower endof a pipe string (not shown) for lowering this element 17 and itsdepending casing string 21- into the Well from a suitable operationalplatform positioned above the well.

The lower and intermediate sections of the housing, 12 and 13respectively, are provided with seating surfaces 23 and 24,respectively, on the outer surfaces near the upper ends thereof whichare adapted to seat thereon cooperating seating surfaces 25 and 26formed on the inner surfaces near the lower ends of the intermediate andupper housing sections 13 and 14, respectively. Seal means 27 and 28 areprovided between the cooperating seating faces.

Lower locking screws or bolts 31 are horizontally positioned in athreaded manner within the lower end of the intermediate section ofhousing 13 and arranged to extend through the wall thereof and intocooperating recesses 32 formed in the wall of the lower housing section12 near the top thereof. In a like manner, the top section 14 of thehousing is provided with upper lock screws 33 adapted to seat inrecesses 34 in the wall of the intermediate section 13 of housing nearthe top thereof. If desired or necessary, the lock screws 31 and 33 maybe provided with fiuidtight seals 35 and 36. While it is preferred inaccordance with the present invention to employ a wellhead having lowerand intermediate sections of a housing 12 and 13, respectively, it isquite ap parent that the intermediate and lower sections 13 and 12 couldbe formed as a single element in which case the lower locking screws 31could be eliminated. However, as a safety precaution in underwaterwellhead structures, the housing employs lower and intermediate sections12 and 13 secured together by means of the lower locking screws 31 whichare preferably made of an alloy carbon steel or other suitable materialso that they can be drilled out in the event that the upper lock screws33 become wedged or corroded in a manner so that they cannot bewithdrawn from their seating position in order to remove the top section14 of the housing from the wellhead.

Formed on the inner wall of the casing hanger 17 near the top thereof isa landing surface 37 adapted to receive and seat'thereon a tubing hanger38. The outer surface of the tubing hanger 38 at the lower end thereofis provided with a tapered seating surface'41, preferably provided withseal means 42, such for example as any suitable type of packing'orO-rings. The tubing hanger 38 is adapted to be secured at its lower endto the top of 'a string of tubing 43, for example, byscrew threads. Thetubing string 43 depending from the tubing hanger 38 is concentricallyarranged within the well casing string 21.

Formed within the tubing hanger 38 are a pair of concentrically andvertically arranged and inwardly directed spaced sealing surfaces 44 and45 against which a pair of concentric nipples 46 and 47 are adapted toseal. The lower ends of the nipples 46 and 47 are provided with packingrings 48 and 49 in order to form a fiuidtight seal. Preferably, theportions of the tubing hanger at the top of the sealing surfaces 44 and45 are tapered as at 52 and 53 to facilitate entry of the lower ends ofthe nipples into the top'of the tubing hanger 38. One or more fluid flowpassageways 54 extend vertically through the tubing hanger 38 incommunication between the space between the sealing surfaces 44 and 45and the annulus 55 formed between the outer wall of the tubing'43 andthe inner wall of the casing 21.

Formed in the top of the upper bonnet section 14, which forms theclosure section of thehousing, is a chamber 56. The outer nipple 46 isfixedly secured at its'upper end inside the top section 14 of thehousing in a manner such that the open top end of the nipple 46 is inopen communication with 'the chamber '56 within the housing. chamber 56are closed in any suitable manner by a suitable cover plate 57 which mayform the lower flange of The top section, 14 of the housing and the 43,be removed and the apparatus would still function in the same way. Aseal 73 is provided between the top cover plate 73 and its mating flange74 at the top of the upper section of the housing.

A set of control screws 75 are threadedly mounted in a fluidtight mannerwithin screw holders 76 which are in turn fixedly secured into the wallof the intermediate section 13 of the housing so that theinwardly-directed end of the screw 75 is adapted to engage acircumferential groove 77 formed in the outer wall of the tubing hanger38 so as to hold the tubing hanger in the wellhead and prevent it frombeing raised off its seat 37 by means of well pressure. Similar lowercontrol screws 80 mounted in holders 81 are provided whereby thescrews80 can be extended toengage a circumferential groove 82 formed inthe outer surface of the casing hanger 17.

Aligning means must be provided between the various sections of thehousing 12, 13 and 14 so that the lock screws 31 and 33 holding thesections together are in register with their respective recesses 32'and34 at the time the lock screws engage the recesses. The recesses 32 and34 are no larger than the tapered end of the lock a production tree (notshown) which is secured to the top of the well. The production tree mayinclude a pair of How conduits 60 and 61 having valves 62 and 63 locatedtherein, respectively. The cover plate 57'is conr nected in any suitablemanner to the top-section 14 of the housing, as by bolts 63'and 64.Passing through the 7 cover plate 57 in communication with thefiowconduits 60 and 61 are a pair of flow passageways 66 and 67.

The flow passageway 67 is in communication between the flow conduit 61,and thence through chamber 56, annular space 69 and flow passageways 54,with the annular space 55 between the tubing string 43 and, the casingstring 21. Thus, means are provided for measuring the casing pressurewithin the well or for extracting or injecting fluid into the annulus 55between the tubing string 43 and the casing string 21. By providingconcentric tubing and casing strings 43 and 21, respectively,'below thewellhead, smaller diameter pipe may be employed than would be needed iftwo parallel tubing strings were run down the well. Additionally, thecasingstring 21 has considerably more strength than a tubing string 43..

screws 31 and 33so that an area contact is established between the lockscrews and the housing section in which they are positioned, thussubstantially eliminating any plastic flow of metal as would take placein line contact between the two elements. 1

Any suitable means for aligningone section with respect to another maybe employed. In the particular arrangement illustrated, the lowerportion of the top or bonnet section of the housing 14 is provided withtapered slots 83 which align themselves on pins formed by the screwholder 76 mounted on the outside of the intermediate section 13 of thehousing. In a like manner, the lower portion of the intermediate section13 of the housing is provided with aligning slots 84 adapted to receivetherein the screws holder 81 which is secured to the lower section 12 ofthe housing. If desired, the portions of the housing sections betweenthe aligning slots may be interconnected by ring members 85 and 86 togive more strength to the assembly. In using the wellhead of the presentinvention on an underwater well, the well is first drilled in the oceanfloor and the lower section 12 of the housing being securely fastened tothe surface casing 11 is lowered into place on the ocean floor in itsposition there when the surface casing is cemented in a conventionalmanner. The intermediate section 13 of the housing is also normallyconnected to the lower section 12 of the housing at this of the tubinghanger 38 provides straight through fluid- V tight communication betweenthe tubing string 43 and the flow passageway 66 to the flow conduit-60in the production tree on top of the wellhead. Toreduce the diameter ofthe equipment needed in the present wellhead, sealing surfaces 44 and45-are preferably axially displaced one from the other as illustrated togive a larger flow passage between.

Secondary seals and 71 are provided between the top and intermediatesections and between the intermediate and lower sections of the housing,respectively. 'It is realized that with seals '28 and 70 being employedin the upper part of the housing, the outer nipple 46 could time, beingsecured together by :lock screws 31. The control screws and are carriedby the intermediate and lower sections 13 and 12, respectively, ofthehousing with the screws being in a retracted position.

In running the lower section 12 and the intermediate section 13 of thehousing to the ocean floor together with the surface casing 11 which isrun into the well, a drilling bonnet 99 (FIGURE 2) replaces the top orbonnet section 14 (FIGURE 1) and is secured to the intermediate section13 of the housing by means of a series of bolts 91 (FIGURE 2) which areidentical to bolts 33 (FIGURE 1) and are positioned to seat within thesame recesses 34. Drilling operations are continued with the drillingbonnet 91) in place on the top of the housing. The drilling bonnet 'mayhave conventional equipment secured thereto such as a blowout preventer92, remotely-controlled connector apparatus 93 and a fluid conductorpipe 34 through which drill pipe or other pipe strings (not shown) mayextend at diiierent periods during the drilling operations.

When the time has arrived in drilling operations to install the casingstring 21, the casing suspension hanger 17 is connected to the top ofthe casing string 21 and the entire apparatus is lowered, as from anoperational platform or barge on the surface of the water, in anysuitable well known manner, as by means of a pipe string, down theintermediate and lower sections of the housing until the casing hanger17 is seated on the shoulder 16 within the lower section 12 of thehousing. Subsequently, at the desired time, the tubing hanger 38 issecured to the top of the tubing string 43 and run in the well in thesame manner until the tubing hanger 38 is seated on the landing surface37 at the top of the casing hanger. Hold down screws 86) are preferablycaused to engage and secure the casing hanger 17 immediately after thelatter has been landed. Likewise, hold-down screws 75 are caused toengage and secure the tubing hanger 38 after the latter has been landedin assembly.

It is of importance to note that under normal conditions lock screws 31are not manipulated during the well completion operation inasmuch astheir only function is to secure parts 13 and 14 in assembly and theseare preferably screwed together prior to being installed and are notdisconnected during normal completion practices.

The upper section of bonnet 14 is then lowered, as by means of adetachable pipe string, onto the top of the intermediate section 13 andthe nipples 46 and 47 are stabbed into the tubing hanger 38 so as toform a fluidtight seal with the sealing surfaces 44 and 45,respectively. All of the lock screws 33 are then rotated in any suitablemanner, as by means of the apparatus disclosed in copending patentapplication, Serial No. 24,558, filed April 25, 1960, in the event thatthe water is too deep to use divers. The screws are tightened until thecomponents of a wellhead have been secured together in a fluidtight andpressuretight manner. At the time the bonnet 14 is lowered into place,the cover plate 57 and the production tree (not shown) including theflow conduits 60 and 61 which have been previously attached to the topof the bonnet, are installed.

We claim as our invention:

1. A wellhead assembly for supporting a casing string and a tubingstring disposed within said casing string, both of said stringsextending into a well bore and depending from said wellhead assembly,said Wellhead assembly comprising a housing member having an open upperend,

landing surface means formed in said housing member for supporting atubing hanger thereon with a tubing string depending from said tubinghanger,

closure means releasably connectible to said housing member for closingthe upper end thereof, I

first passageway means defined by said wellhead assembly and extendingthrough said closure means in communication between said tubing stringdepending within said housing member and the space above said closuremeans, portions of said first passageway means being defined byseparable portions of said wellhead assembly,

first conduit means forming a portion of said separable portions of saidwellhead assembly defining said first passageway means,

a connector means carried on one end of said first conduit means withinsaid housing and engageable through vertically-directed motion bytranslation with a mating portion of said other separable portion, and

second passageway means defined by said wellhead assembly and extendingthrough said closure means in communication between the space above theclosure means and a space within said wellhead assembly formed betweensaid tubing string and said casing string depending from said wellheadassembly.

2. The apparatus of claim 1 including the second conduit means spacedfrom said first conduit means and forming a portion of said secondpassageway means.

3. The apparatus of claim 1 wherein a portion of said first conduitmeans comprises downwardly-extending nipple means fixedly positionedwithin said housing mem her, the lower end of said nipple means being inaxial alignment with the landing surface means in said housing forsupporting a tubing hanger.

4. The apparatus of claim 1 wherein the outer surface of said housingmember tapers inwardly and upwardly near the top thereof forming atapered landing surface for said closure means, and wherein said closuremeans has a downwardly-extending portion adapted to fit down over thetop of said housing member, there being formed on the inner surface ofsaid downwardly-extending portion of said closure means an inwardly andupwardly tapering seating surface at an angle to cooperate with saidlanding surface of said housing member.

5. The apparatus of claim 4 including connecting means for securing saidclosure means to said housing member, wherein said connector meanscomprises a plurality of inwardly extending locking screws carried bysaid closure means around the periphery and adapted to extend throughthe wall of the downwardly-extending portion thereof and extendible intomating recesses formed in the adjacent outer wall of said housingmember.

6. A wellhead assembly for supporting a casing string and a tubingstring concentrically-disposed within said casing string, both of saidstrings extending into a well bore and depending from said wellheadassembly, said wellhead assembly comprising a housing member having anopen upper end and defining a cross-over chamber formed therein whensaid housing member is closed,

unitary closure means having a pair of laterally dis-' placed portstherethrough and being releasably connectible to said housing member forclosing the upper end thereof,

first nipple means carried by said wellhead assembly in communicationbetween a tubing string depending from said housing member and throughone of said ports in said closure means with the space thereabove,

second nipple means spaced apart from said first nipple means carried bysaid wellhead assembly in communication, through the cross-over chamberwithin said wellhead assembly and through the other of said ports insaid closure means, between the space above the closure means and aspace formed between a tubing string and a casing string depending fromsaid housing member, and

said lower end of said unitary closure means and said lower end of saidfirst nipple means being each engageable through vertically-directedmotion by translation with a mating portion of said wellhead assembly.

7. A wellhead assembly for supporting a tubing string and a casingstring within a well and providing vertical discharge connections fromsaid tubing string and easing string, said wellhead assembly comprisinga housing structure, said housing being formed in at least a lowersection and a top unitary closure section, said lower section havingseating means formed near the upper end thereof adapted to seatcooperating seating means of said closure section,

first support means carried by the lower section of said housing,

casing suspension means supported by said first support means of saidhousing,

second support means carried within said lower section of said housing,

tubing suspension means supported by said second support means,

casing means secured at one end to said casing suspension means,

tubing means secured at one end to said tubing suspension means anddepending therefrom within said casing means,

connector means carried by one of said sections of said housing forsecuring said sections together,

said closure section defining at least two 'fiuid passageways,

first conduit means in said housing in communication between said tubingmeans and one of the fluid passageways in the closure section,

second conduit means in said housing in communication between saidsuspended casing means and a second'of said fluid passageways in theclosure sec-, tion, and

said lower end of said unitary closure means and said lower ends of saidfirst and second conduit means being each engageable throughvertically-directed motion by translation with a correlative portion ofsaid wellhead assembly.

8. A Wellhead assembly for supporting a tubing string said housingcross-over chamber being formed above said tubing suspension means,

nipple means having the upper end thereof secured to the closure sectionand extending downwardly through said chamber, the lower end of saidnipple means being positioned through vertically-directed motion bytranslation in fluid communication with the top of said tubing means,

connector means carried by one of said sections of said housing forsecuring said sections together,

said closure section defining two vertical fluid passageways,

one of said passageways being in communication with the upper end of thenipple means and the other of said passageways being in communicationwith the cross-over chamber and conduit means in said housing.

and a casing string within a well and providing parallel verticaldischarge connections from said tubing string and easing string, saidwellhead assembly comprising a housing structure, said housing beingformed in at least a lower section and a top closure section, said lowersection having seating means formed near the References Cited by theExaminer UNITED STATES PATENTS upper end thereof adapted to seatcooperating seat- $333 u ing means 0f Said Closure Sectio Dean a firstlanding means for casing suspension means carried 1849374 3/32 M CEV 285144 by the lower section of said housing, 1941467 1/34 Fwseky 285:137casing suspension means supported on said first landing 1983938 v12/34 g285 140 means 2,034,698 V 3/36 Hild. second landing means for tubingsuspension means 2 082 413 6/37 Mu d1 V 285 A01 f i sa1d housmg2,118,094 5/38 McDonough 2s5-140 tubing suspension means supported bysa1d second landoO- 2 134 200 10/38 Pivoto 166 86 ing means, casingmeans secured at one end to said casing suspeng zi g; t means 2,584,2832/52 Oliver 285 4o4 ubing means secured at one end to said tublngsuspen- 2 983 318 5/61 Baker 166 89 sion means, w said tubing suspensionmeans having vertical fluid flow 3004778 10/61 Wflhams' passageway meansin addition to the bore there- FOREIGN PATENTS through, i said housingdefining a cross-over chamber and con- 480,817 3/38 Great Bmamduit meanstherein in communication with the flow 40 passageway means through saidtubing suspension CARL W. TOMLIN, Primary Examiner.

7 means,

1. A WELLHEAD ASSEMBLY FOR SUPPORTING A CASING STRING AND A TUBINGSTRING DISPOSED WITHIN SAID CASING STRING, BOTH OF SAID STRINGSEXTENDING INTO A WELL BORE AND DEPENDING FROM SAID WELLHEAD ASSEMBLY,SAID WELLHEAD ASSEMBLY COMPRISING A HOUSING MEMBER HAVING AN OPEN UPPEREND, LANDING SURFACE MEANS FORMED IN SAID HOUSING MEMBER FOR SUPPORTINGA TUBING HANGER HTEREON WITH A TUBING STRING DEPENDING FROM SAID TUBINGHANGER, CLOSURE MEANS RELEASABLY CONNECTIBLE TO SAID HOUSING MEMBER FORCLOSING THE UPPER END THEREOF, FIRST PASSAGEWAY MEANS DEFINED BY SAIDWELLHEAD ASSEMBLY AND EXTENDING THROUGH SAID CLOSURE MEANS INCOMMUNICATION BETWEEN SAID TUBING STRING DEPENDING WITHIN SAID HOUSINGMEMBER AND THE SPACE ABOVE SAID CLOSURE MEANS, PORTIONS OF SAID FIRSTPASSAGEWAY MEANS BEING DEFINED BY SEPARABLE PORTIONS OF SAID WELLHEADASSEMBLY, FIRST CONDUIT MEANS FORMING A PORTION OF SAID SEPARABLEPORTIONS OF SAID WELLHEAD ASSEMBLY DEFINING SAID FIRST PASSAGEWAY MEANS,A CONNECTOR MEANS CARRIED ON ONE END OF SAID FIRST CON-